Rift Valley fever (RVF) is a viral disease of humans and livestock that can cause mild to severe symptoms. The mild symptoms may include: fever, muscle pains, and headaches which often last for up to a week. The severe symptoms may include: loss of sight beginning three weeks after the infection, infections of the brain causing severe headaches and confusion, and bleeding together with liver problems which may occur within the first few days. Those who have bleeding have a chance of death as high as 50%.
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains—particularly in the back—and headaches. Symptoms typically improve within five days. In about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is increased.
West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. Recovery may take weeks to months. The risk of death among those in whom the nervous system is affected is about 10 percent.
Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. It is frequently asymptomatic; if symptoms appear they typically begin 3 to 14 days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin itching and skin rash. Recovery generally takes two to seven days. In a small proportion of cases, the disease develops into severe dengue with bleeding, low levels of blood platelets, blood plasma leakage, and dangerously low blood pressure.
Mpox is an infectious viral disease that can occur in humans and other animals. Symptoms include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. The illness is usually mild, and most infected individuals recover within a few weeks without treatment. The time from exposure to the onset of symptoms ranges from three to seventeen days, and symptoms typically last from two to four weeks. However, cases may be severe, especially in children, pregnant women, or people with suppressed immune systems.
Chikungunya is an infection caused by the Chikungunya virus (CHIKV). The disease was first identified in 1952 in Tanzania and named based on the Kimakonde words for "to become contorted".
The West Nile virus quickly spread across the United States after the first reported cases in Queens, New York, in 1999. The virus is believed to have entered in an infected bird or mosquito, although there is no clear evidence. The disease spread quickly through infected birds. Mosquitoes spread the disease to mammals. It was mainly noted in horses but also appeared in a number of other species. The first human cases usually followed within three months of the first appearance of infected birds in the area except where cold weather interrupted the mosquito vectors. Since the virus has become widely established in the U.S., an average of 130 deaths a year have occurred.
Eastern equine encephalitis (EEE), commonly called Triple E or sleeping sickness, is a disease caused by a zoonotic mosquito-vectored Togavirus that is present in North, Central, and South America, and the Caribbean. EEE was first recognized in Massachusetts, United States, in 1831, when 75 horses died mysteriously of viral encephalitis. Epizootics of EEE in horses have continued to occur regularly in the United States. It can also be identified in donkeys and zebras. Rarely, it can also infect humans. Due to the rarity of the disease, its occurrence can cause economic impact beyond the cost of horses and poultry. EEE is found today in the eastern part of the United States and is often associated with coastal plains. It can most commonly be found in East Coast and Gulf Coast states. In Florida, about one to two human cases are reported a year, although over 60 cases of equine encephalitis are reported. In years in which conditions are favorable for the disease, the number of equine cases is over 200. Diagnosing equine encephalitis is challenging because many of the symptoms are shared with other illnesses and patients can be asymptomatic. Confirmations may require a sample of cerebrospinal fluid or brain tissue, although CT scans and MRI scans are used to detect encephalitis. This could be an indication that the need to test for EEE is necessary. If a biopsy of the cerebrospinal fluid is taken, it is sent to a specialized laboratory for testing.
Oropouche fever is a tropical viral infection which can infect humans. It is transmitted by biting midges and mosquitoes, from a natural reservoir which includes sloths, non-human primates, and birds. The disease is named after the region where it was first discovered and isolated in 1955, by the Oropouche River in Trinidad and Tobago. Oropouche fever is caused by the Oropouche virus (OROV), of the Bunyavirales order of viruses.
Oropouche orthobunyavirus (OROV) is one of the most common orthobunyaviruses. When OROV infects humans, it causes a rapid fever illness called Oropouche fever. OROV was originally reported in Trinidad and Tobago in 1955 from the blood sample of a fever patient and from a pool of Coquillettidia venezuelensis mosquitoes. In 1960, OROV was isolated from a sloth and a pool of Ochlerotatus serratus mosquitoes in Brazil. The virus is considered a public health threat in tropical and subtropical areas of Central and South America, with over half a million infected people as of 2005. OROV is considered to be an arbovirus due to the method of transmission by the mosquitoes Aedes serratus and Culex quinquefasciatus among sloths, marsupials, primates, and birds.
Zika fever, also known as Zika virus disease or simply Zika, is an infectious disease caused by the Zika virus. Most cases have no symptoms, but when present they are usually mild and can resemble dengue fever. Symptoms may include fever, red eyes, joint pain, headache, and a maculopapular rash. Symptoms generally last less than seven days. It has not caused any reported deaths during the initial infection. Mother-to-child transmission during pregnancy can cause microcephaly and other brain malformations in some babies. Infections in adults have been linked to Guillain–Barré syndrome (GBS).
Zika virus is a member of the virus family Flaviviridae. It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus. Its name comes from the Ziika Forest of Uganda, where the virus was first isolated in 1947. Zika virus shares a genus with the dengue, yellow fever, Japanese encephalitis, and West Nile viruses. Since the 1950s, it has been known to occur within a narrow equatorial belt from Africa to Asia. From 2007 to 2016, the virus spread eastward, across the Pacific Ocean to the Americas, leading to the 2015–2016 Zika virus epidemic.
As of 2010, dengue fever is believed to infect 50 to 100 million people worldwide a year with 1/2 million life-threatening infections. It dramatically increased in frequency between 1960 and 2010, by 30 fold. This increase is believed to be due to a combination of urbanization, population growth, increased international travel, and global warming. The geographical distribution is around the equator with 70% of the total 2.5 billion people living in endemic areas from Asia and the Pacific. Many of the infected people during outbreaks are not virally tested, therefore their infections may also be due to chikungunya, a coinfection of both, or even other similar viruses.
Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after infection. The first symptoms are usually fever, sore throat, muscle pain, and headaches. These are usually followed by vomiting, diarrhoea, rash and decreased liver and kidney function, at which point some people begin to bleed both internally and externally. It kills between 25% and 90% of those infected – about 50% on average. Death is often due to shock from fluid loss, and typically occurs between six and 16 days after the first symptoms appear. Early treatment of symptoms increases the survival rate considerably compared to late start. An Ebola vaccine was approved by the US FDA in December 2019.
An epidemic of Zika fever, caused by Zika virus, began in Brazil and affected other countries in the Americas from April 2015 to November 2016. The World Health Organization (WHO) declared the end of the epidemic in November 2016, but noted that the virus still represents "a highly significant and long term problem". It is estimated that 1.5 million people were infected by Zika virus in Brazil, with over 3,500 cases of infant microcephaly reported between October 2015 and January 2016. The epidemic also affected other parts of South and North America, as well as several islands in the Pacific.
In October 2013, there was an outbreak of Zika fever in French Polynesia, the first outbreak of several Zika outbreaks across Oceania. With 8,723 cases reported, it was the largest outbreak of Zika fever before the outbreak in the Americas that began in April 2015. An earlier outbreak occurred on Yap Island in the Federated States of Micronesia in 2007, but it is thought that the 2013–2014 outbreak involved an independent introduction of the Zika virus from Southeast Asia. Investigators suggested that the outbreaks of mosquito-borne diseases in the Pacific from 2012 to 2014 were "the early stages of a wave that will continue for several years", particularly because of their vulnerability to infectious diseases stemming from isolation and immunologically naive populations.
This article primarily covers the chronology of the 2015–16 Zika virus epidemic. Flag icons denote the first announcements of confirmed cases by the respective nation-states, their first deaths, and relevant sessions and announcements of the World Health Organization (WHO), and the U.S. Centers for Disease Control (CDC), as well as relevant virological, epidemiological, and entomological studies.
On 20 January 2016, the health minister of Angola reported 23 cases of yellow fever with 7 deaths among Eritrean and Congolese citizens living in Angola in Viana municipality, a suburb of the capital of Luanda. The first cases were reported in Eritrean visitors beginning on 5 December 2015 and confirmed by the Pasteur WHO reference laboratory in Dakar, Senegal in January. The outbreak was classified as an urban cycle of yellow fever transmission, which can spread rapidly. A preliminary finding that the strain of the yellow fever virus was closely related to a strain identified in a 1971 outbreak in Angola was confirmed in August 2016. Moderators from ProMED-mail stressed the importance of initiating a vaccination campaign immediately to prevent further spread. The CDC classified the outbreak as Watch Level 2 on 7 April 2016. The WHO declared it a grade 2 event on its emergency response framework having moderate public health consequences.
East Africa had a regional outbreak of Rift Valley fever in late 2006 that affected Kenya, Somalia, and Tanzania. During outbreak, 1062 people were infected with Rift Valley fever and 394 people died between December 2006 and December 2007. Rift Valley fever (RVF) is caused by a phlebovirus in the Bunyavirales order which is transmitted by mosquito bite and contact with infected animal blood; it mainly infects livestock that come into infectious contact with a viral reservoir but human beings can also be infected. The outbreak began after a heavy El Niño rain season across East Africa left greater than usual breeding ground for Aedes aegypti mosquitos, with particularly heavy rainfall over eastern Kenya, central Tanzania, and southern Somalia. While most people infected with the virus experience a relatively mild, flu-like illness without hospitalization, around 8% will develop a severe illness that can include eye disease, encephalitis, hemorrhagic fever and death. During this outbreak, of the 1,062 hospitalized, laboratory-confirmed RVF cases assays, 37% died.
The 2022–2023 mpox outbreak in North America is a part of the outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak reached North America on 18 May 2022, when the United States reported their first case of mpox. As of 23 August 2022, 20 North American countries and territories have confirmed cases.
